1. Field of Invention
This invention relates generally to non-destructive evaluation of tubes and more particularly to non-destructive evaluation of a tube using an ultrasonic sensor.
2. Description of Related Art
Processing plants, such as power generation petrochemical and plants for example, make extensive use of metal tubing for delivering steam and other fluids to various process steps. Commonly, such tubes are constructed by welding together sections of tubing. In most applications, and specifically in safety critical applications, each and every weld must be inspected to confirm the integrity of the weld. Such inspections may be performed during the construction or commissioning of a plant, but there is also a need for ongoing periodic inspection of welds to look for signs of corrosion and/or cracking, for example.
In many plants pluralities of tubes are run in close proximity to each other, often so closely spaced apart that access to the tube for performing an inspection of the weld may be difficult. While it is convenient to use ultrasonic non-destructive evaluation techniques for examining defects in many types of metal structures, the accessibility has limited the use of ultrasonic examination for inspecting tubes.
Accordingly, other inspection techniques such as gamma radiography have typically been used to perform such inspections. Gamma radiography involves the use of radioactive isotopes, and during radiographic inspections, radiographic shielding barriers must generally be erected to protect personnel from harmful radiation. Accordingly, the work of welders and other construction workers may be interrupted when it becomes necessary to clear an area in proximity to a tube being inspected.
In general the use of radioactive inspection techniques may cause unacceptable health and safety risks, and regardless of storage, handling, and transportation practices that may be implemented, human error may still occur resulting in accidents.
Accordingly there is a need for improved methods of inspection of tubes.